Capsules have been used for many years as an oral delivery form for various healthcare products, including medicines, vitamins or dietary supplements. Initially, the filling products were drugs in powdered or granular form, and the filled capsule provided a unit dose that effectively masked the bitter taste of drugs in an easy-to-swallow dosage form, being effective rapidly. Later on, taking profit from the versatility of this particular dosage form, it was proposed to enlarge the type of filling product to more complex formulations, to multiparticulates drugs and more recently to liquid products.
Capsules are generally made of two parts, i.e. a cylindrical body having a rounded bottom and a rounded cap mounted around the free end of the body. These capsules are generally made from gelatine, HPMC, pullulan or others.
The production of such capsules includes the preparation of the two parts of the capsules and the filling of such capsules. The two parts may be provided as loose parts or as empty capsules. The filling of the capsules generally occurs after some control of the empty parts (see for example U.S. Pat. No. 5,238,124 or U.S. Pat. No. 6,539,686) and/or some orientation of such parts (see for example U.S. Pat. No. 5,417,030). The filling of the capsules is made in machines which are generally called filling machines, wherein the filling product is dosed into the body and the cap is then telescopically mounted onto this body.
One problem with such two-piece capsules is that the filling product, especially when it is a fine powdered product or a low viscosity liquid product, may escape or leak from the assembled capsules, between the filling operation and the moment when the capsule is to be used; one consequence of such leaks is that the actual quantity of drug contained in the capsule when it is used is no longer the proper intended dose.
Further, it is even possible that the leaking product leads to some deterioration of the package including the capsules or of the other capsules in the package or may lead by contamination to some unwanted chemical reaction with external products. Thus, it is important in particular to prevent such leakage during transport and storage of the capsule within its package (for example a blister pack). It may thus be understood that an essential part of the general process of filling a capsule, especially when the filling product is a liquid, is the ability to then effectively strengthen the connection of the two parts. Various methods are available, including attempts to provide the body and the cap with complementary geometrical features which result in some locking thereof, or some ultrasonic welding (see for example EP-0 135 372).
However, especially for fine powdered or liquid products, the following processes are preferred: i) “sealing” using a sealing solution which provides when dried a sealing between the adjoining surfaces of the two parts and. ii) “banding” using an additional gelatine band around the circumference of the capsule at the limit of the two parts
Examples of sealing solutions are given in EP-0 116 744, U.S. Pat. No. 4,584,817, U.S. Pat. No. 4,724,019, U.S. Pat. No. 4,734,149, U.S. Pat. No. 4,940,499 or DE-38 00 852. Such sealing machines generally include some conveying devices for wetting the capsules with some appropriate sealing fluid and then drying same before ejecting the sealed capsules via a discharge chute.
Later on there may exist some further processing, such as weighing (see for example U.S. Pat. No. 4,204,951) or controlling (see for example U.S. Pat. No. 6,162,998); the capsules are often eventually packed within blisters.
Filling and sealing machines are generally different machines with independent inlets and outlets, and sealing machines generally comprise inlet elements consisting of a hopper where the capsules to be sealed are entered with randomly distributed orientations. In order to ensure the precision of the seal, some sealing machines comprise, after the input hopper, orientation rectifying stations (see for example above cited U.S. Pat. No. 4,584,817 or U.S. Pat. No. 4,940,499) so as to provide the capsules to the seating/banding station in a given orientation. However, in most cases, the transfer of the filled capsules from the filling machine to the sealing machine is made without any control of the orientation of the capsule, since the filled capsules are generally discharged into containers such as baskets or onto classical conveyors where the capsules take any orientation, whereas it is easy to understand that the risk of leakage is increased when the capsules are tumbled cap downwards. It is here to be noted that a specific consequence of a leak at that moment is that the leaking product, especially the product remaining between the facing surfaces of the cap and body, may prevent a proper sealing in the following station. In addition, it is to be noted that the need to rectify the orientation of the capsules within the sealing machine leads to possible slight deformation because of the squeeze effect required therefore, increasing further the risk for leakage.
There has been proposed, in above cited U.S. Pat. No. 4,724,019, a sealing machine where no orientation rectification is required, whereas no risk of tumbling exists between the preceding filling machine and the inlet within this sealing machine. But this result is achieved by a direct connection of the inlet of the sealing machine to the outlet of the filling machine. More precisely, groups of capsules are discharged intermittently from capsule-containing compartments located in movable raceway elements of this filling machine. However, it is clear that this requires that both machines are designed so as to allow a direct connection (this requires that the machines cannot be selected and bought on the basis of their individual performances only), and enough space shall be available for locating both machines in a line.
It shall be mentioned here that, for the sake of productivity, the capsules are generally processed in groups of capsules distributed in arrays which are generally different from a machine to the other, so that there is a strong restriction in the choice of the machines to select a combination of machines allowing a direct connection.